Article. 37. Marriages
between the following are incestuous and void from the beginning, whether the
relationship between the parties be legitimate or illegitimate:

Between ascendants and descendants of any
degree; andBetween brothers
and sisters, whether of the full or half blood. (81a)

Article. 38. The following marriages
shall be void from the beginning for reasons of public policy:

Between collateral blood relatives, whether
legitimate or illegitimate, up to the fourth civil degree;Between step-parents and
step-children;Between
parents-in-law and children-in-law;Between the adopting parent and the adopted child;Between the surviving spouse of the
adopting parent and the adopted child;Between the surviving spouse of the adopted child and
the adopter;Between an
adopted child and a legitimate child of the adopter;Between adopted children of the same adopter;
andBetween parties where
one, with the intention to marry the other, killed hat other person's spouse, or
his or her own spouse. (82a)

Marriage between ascendants and descendants
in straight line or between siblings are forbidden.Marriage between adopting parent and adopted child is
also forbidden, unless the child is adopted by someone else later, and
permission is given by a civil servant to marry the former adopting parent or
his or hers relative.